The present invention relates to a device for triggering an air bag system adapted to protect a passenger upon collision of a vehicle such as an automobile, and more particularly to such an air bag triggering device including a link mechanism operatively connecting a sensor with a slide member so that the device is inactive when an impact or vibration smaller than a predetermined limit is applied, and is operable from a reference position at all times.
In order to protect a passenger in an automobile upon collision thereof, the present inventors have already developed such an air bag triggering device employing a high-pressure gas as a pressure source. This air bag triggering device is disclosed in Japanese Laid-Open Utility Model Publication No. 61-153652.
As shown in FIG. 4, this conventional air bag triggering device includes an inertia weight member 21 serving as a sensor, a slide member 22, an operating lever 23, a push rod 24, a ball valve 25, etc. When an impact is applied to the air bag triggering device as a consequence of collision, the inertia weight member 21 is moved in a direction of the arrow A, and a hook portion 21a formed at one end of the inertia weight member 21 is released from a latching portion 22a of the slide member 22 biased by a spring 26. As a result, the slide member 22 is moved by a restoring force of the spring 26 in a direction of the arrow B. Then, the slide member 22 strikes the operating lever 23 to pivot the latter about a pivotal shaft 27. As a result, the operating lever 23 strikes the push rod 24. The push rod 24 is formed at its front end with a wedge-shaped portion 24a which is adapted to push a ball 28 of the ball valve 25. Then, the ball 28 is disengaged from a valve seat 29 of the ball valve 25, thus introducing the high-pressure gas in a high-pressure cylinder 30 into an air bag (not shown) along the arrows C.
However, the aforementioned device has the following problems. Generally, various impacts may be applied to an automobile or the like in addition to impacts caused by collisions. Sometimes, the engaged position between the latching portion 22a of the slide member 22 and the hook portion 21a of the inertia weight member 21 can be shifted from a set position depending on the conditions of vibration and friction. Accordingly, there is a possibility that the air bag triggering device cannot start its operation from a reference position. Furthermore, it is difficult to adjust the sensitivity of the inertia weight member 21 serving as the sensor, causing the difficulty in ensuring the triggering accuracy of the device.